# Umbrella sampling output

**URL:** <https://gromacs.bioexcel.eu/t/umbrella-sampling-output/4285>\
**Category:** User discussions\
**Created:** [June 10, 2022, 3:44am UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-output/4285 "2022-06-10T03:44:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![tan1](https://avatars.discourse-cdn.com/v4/letter/t/b3f665/32.png) [@tan1](https://gromacs.bioexcel.eu/u/tan1)\
**Post date:** [June 10, 2022, 3:44am UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-output/4285/1 "2022-06-10T03:44:15Z")

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GROMACS version:2019.2  
GROMACS modification: Yes/No  
After performing umbrella sampling on **wild-type Aβ42 protofibril** , I have obtained a graph for PMF. It has many fluctuations when i compare it to the graph in the tutorial. This is the image of my PMF graph  
 ![photo](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/1/190b73c18eebd8b8d2616ff2a36d06e5b8a75c9b.png)  
X AXIS: REACTION COORDINATE, Y AXIS: PMF

P.S: Post running the command gmx wham -it tpr-files.dat -if pullf-files.dat -o -hist -unit kCal  
I got many warnings like no data-point in bin 162(z = 3.16453) you may not get a reasonable profile check your histogram!

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [June 10, 2022, 4:10am UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-output/4285/2 "2022-06-10T04:10:32Z")

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> [@tan1](#):
>
> no data-point in bin 162(z = 3.16453)

This means you probably did not choose very good initial configurations as the basis for your windows, leaving gaps in the sampling along the reaction coordinate.